Temporal changes in the taxonomic and functional diversity of fish communities in shallow Chinese lakes: the effects of river–lake connections and aquaculture

1. Habitat modification by humans has severe impacts on the biotic and abiotic components of freshwater ecosystems. In China, shallow lakes in the Yangtze River basin are facing major habitat modification owing to the loss of their natural connections with rivers and the development of aquaculture.
2. In this study, temporal data (ranging from 1970 to 2010) from a set of lakes (n = 8) were used to quantify the abiotic and biotic consequences (i.e. taxonomic and functional diversity of fish communities) of such human activities. There were significant abiotic changes that mainly occurred after the 1990s. Specifically, water transparency decreased and the total nitrogen content of the lakes increased considerably.
3. A trend (although not significant) was detected towards a decrease in fish species richness over the period studied. The taxonomic dissimilarity (i.e. beta‐diversity) among fish communities decreased significantly over the years, indicating a strong homogenization of the fauna across the lakes.
4. In addition, it was found that fish functional diversity has decreased in most lakes since the 1970s. In particular most migratory fish species with long life‐spans and large body size disappeared from the lakes, hence contributing substantially to the observed decrease in functional diversity.
5. Based on the findings, it is argued that both the abiotic and biotic integrity of the lakes were seriously affected after the lakes lost their connections to the rivers. It would therefore be helpful to reconnect the lakes to rivers with wise sluice‐gate management, and regulate fishery activities in those lakes to restore fish diversity.

Copyright © 2013 John Wiley & Sons, Ltd.     

Complexity of river ciliate communities at a national park highlights the need for microbial conservation

1. Microorganisms play pivotal roles in aquatic ecosystems. Free‐living protists are the main components of the eukaryotic microbial communities at the base of freshwater ecosystems. Ciliate grazing channels a large proportion of organic matter into multicellular organisms. Surprisingly, ciliates and other microorganisms are neglected in global conservation schemes.
2. Interstitial ciliates were sampled in three sites of varying human pressure on the River Manzanares (La Pedriza National Park, Spain). Abundances of trophic groups and species were adjusted to a generalized linear model (GLM Poisson regression).
3. Ciliate communities were rich in species (74 morphotypes) and although traditional microscopy retrieved a high number of species that appeared only once or in low numbers, rarefaction analyses estimated much larger species richness. These results illustrate that rarefaction assays are a useful first step for exploring the extent of the ciliate cryptic diversity in freshwater ecosystems.
4. Benthic ciliate communities changed significantly, both spatially and at a short temporal scale. The fluctuating nature of the community was manifested by the presence of many ephemeral species at the same river site, revealing a complex and transient community structure. No significant short‐term changes were observed in the physical–chemical properties. Therefore, even slight differences in the abiotic variables may cause rapid shifts of ciliate species.
5. Overall, human pressure had an effect on the interstitial (or benthic) ciliates that resulted in a reduction of species richness and their abundance.

     

The importance of being natural in a human‐altered riverscape: role of wetland type in supporting habitat heterogeneity and the functional diversity of vegetation

1. Human activities have dramatically affected the status of river ecosystems, mainly by completely altering their natural dynamics. One of the main questions in this regard is: 'How do the origin (natural or artificial) and hydrology (lentic or lotic) of a riverine wetland influence its heterogeneity and the functional diversity of its vegetation?'
2. To answer this question, data from 60 wetlands were collected along the Oglio River (northern Italy), a ~700 km² ecosystem that is a typically over‐exploited plain. In order to perform a quantitative assessment of habitat heterogeneity and vegetation diversity, a hierarchical approach was applied to sample sites divided into four functional zones (FZs) according to distinct seasonal inundation patterns (persistently aquatic, riparian, seasonally emergent and lateral zones).
3. Plant communities were randomly surveyed in each FZ by using five replicates of 4 m² plots for aquatic and herbaceous plant communities and five replicates of 64 m² plots for woody and shrub communities. Data on species cover were estimated by standard methods (geometric‐centered scale)
4. The highest values of heterogeneity (FZs per site) and vegetation diversity (plant communities per site) were found in natural lentic sites, whereas natural lotic sites exhibited the lowest values. A clear dependence of plant community assets on wetland origin was detected, thereby confirming the close relationship between heterogeneity and vegetation diversity.
5. Present results highlight the fundamental role played by natural sites in maintaining aquatic and wetland vegetation diversity in human‐altered riverscapes. The pivotal role of water level fluctuations in promoting the diversity and distribution of aquatic and hygrophilous vegetation also clearly emerges.

Copyright © 2015 John Wiley & Sons, Ltd.     

Constrained by aliens,shifting landscape,or poor water quality? Factors affecting the persistence of amphibians in an urban pond network

1. Freshwater communities and especially pond‐breeding amphibians are extremely vulnerable to land‐use change, alien species introductions and the use of pesticides or other toxic chemicals, as reflected in their worldwide decline. Effective conservation and management of ponds requires a better understanding of the biotic and abiotic factors that shape diversity patterns and species distribution, especially in cases of habitat loss
2. The present study aimed to reveal and classify which pond and landscape characteristics are the most important determinants for the occurrence patterns of amphibian species as well as for the overall amphibian species richness in an urban pond network. To achieve this aim, 17 biotic and abiotic variables were measured for 61 ponds and the dataset was analysed by means of a machine‐learning approach, suitability indices and co‐occurrence modelling
3. The highest probability of Triturus macedonicus occurrence was found at fishless artificial and semi‐natural ponds. The persistence of Lissotriton graecus in ponds was predicted by high pond connectivity and the absence of fish reflecting the species dispersive potential. Pelophylax kurtmuelleri showed a higher probability of occurrence with increased pond connectivity and macrophyte cover.
4. Amphibian species richness was higher in fishless ponds with well‐oxygenated waters located in sites with a low to intermediate road density network. Ponds categorized as ‘average’ in terms of newt suitability were more frequently inhabited by fish than Triturus macedonicus. Alien fish species showed negative associations with both newt species, while both newt species showed a positive association between them.
5. The results support the view that conserving a greater number of water bodies with increased landscape connectivity and without any fish presence could provide amphibian species with alternative habitat choices, especially in sites with human pressure where pond stability is at stake owing to continuous landscape changes.

     

GIS analysis reveals the high diversity and conservation value of mollusc assemblages in the floodplain wetlands of the lower Bug River (East Poland)

1. The distribution and species richness of aquatic molluscs were analysed within a 186‐km‐long section of a large (755‐km‐long) lowland river floodplain using GIS maps. Special attention was paid to threatened species.
2. An attempt was made to identify local ‘hotspots’ of molluscan diversity and to determine the most important areas for conservation based on species richness, number of threatened species and indices of synthetic conservation (Q) and centres of population density (ICD).
3. Over four years of investigation, carried out in 176 water bodies, a rich malacofauna was identified: 58 species including 20 of elevated conservation concern.
4. GIS maps revealed numerous ‘hotspots’ of mollusc species richness and higher incidence of threatened species, as well as areas characterized by raised Q and ICD indices.
5. Water body size and hydrological connectivity positively influenced species richness and Q values. The highest values of these variables were found in large water bodies having limited surficial connectivity with the river channel.
6. Species richness, numbers of threatened species, and Q and ICD values were significantly higher in younger permanent water bodies compared with semi‐permanent or temporary ones representing advanced successional stages.
7. Spatial visualization data collected in the study area indicate that the most valuable sites for the conservation of aquatic molluscs include both sides of the river in the lower part of the middle stretch of the lower Bug River valley.

Copyright © 2013 John Wiley & Sons, Ltd.     

Heads you win,tails you lose: Life‐history traits predict invasion and extinction risk of the world's freshwater fishes

1. Freshwater fishes have the distinction of being both a highly imperilled taxonomic group as well as one that has produced many invasive species with widespread ecological impacts. Faced with the difficult task of identifying those species with the greatest need for management action, ecologists have turned to using predictive suites of ecological and life‐history traits to provide reasonable estimates of fish invasion and extinction risk. Whether traits associated with invasiveness are the inverse of those associated with imperillment, known as the ‘two‐sides‐of‐the‐same‐coin’ hypothesis, remains unclear.
2. A global trait analysis (including maximum total body size, longevity, size at maturation, age at maturation, fecundity and egg size) for 6293 freshwater fishes was conducted to examine the trait correlates of species proneness to invasion or extinction. A meta‐analytical procedure was deployed using univariate and multivariate trait analyses that accounted for the effects of shared phylogeny.
3. Mean trait differences (measured as Hedges' d effect size) were found between invasive and threatened species when compared with native species, thus supporting the two‐sides‐of‐the‐same‐coin hypothesis for freshwater fish. Invasive species were characterized by larger body size, greater longevity, delayed maturation and higher fecundity than threatened species. Furthermore, invasive species were found to display greater trait variability compared with threatened species, suggesting that different traits may be selected at different stages of the invasion process (from pathway entrainment to establishment) whereas more specific trait combinations may predispose species to higher extinction risk.
4. The present study demonstrated a strong trait basis to global‐scale invasion risk and extinction vulnerability for freshwater fishes. Given that both time and resources are too limited for detailed species‐by‐species assessments, the results suggest that trait correlates provide a reasonable estimate of invasion and extinction risk that can inform more targeted and proactive conservation strategies.

     

Impacts of Indian waterfern (Ceratopteris thalictroides (L.) Brongn.) infestation and removal on macroinvertebrate biodiversity and conservation in spring‐fed streams in the Australian arid zone

1. Removal of invasive macrophytes is a priority for river managers. However, the ecological effects of macrophyte removal on macroinvertebrate diversity are rarely examined but may be of particular significance in conservation reserves and when threatened species are present.
2. This study investigated the macroinvertebrate fauna inhabiting invasive and native macrophytes in spring‐fed channels in the Millstream‐Chichester National Park, Australia. The effects of waterfern management (periodic hand‐weeding) were examined by comparing assemblages at weeded and unweeded reaches on three occasions.
3. Ceratopteris thalictroides harboured a diverse, insect‐dominated macroinvertebrate assemblage, including the endangered damselfly Nososticta pilbara. Total taxon richness was similar between waterfern and native macrophytes, but macroinvertebrate assemblages differed in the dry season. Damselflies (including N. pilbara) were associated with waterfern‐dominated reaches, whereas dragonfly nymphs were more common among native macrophytes.
4. Weeding altered macroinvertebrate assemblage composition. Some weeded reaches developed assemblages indistinguishable from those in native‐dominated reaches, but others did not. Weeded reaches often supported taxa that were rare or absent from waterfern‐dominated reaches, including suspension feeders, found also in native‐dominated reaches.
5. Odonata are particularly diverse at Millstream, with 18 species recorded. Odonate species richness was significantly lower at weeded reaches than unweeded reaches. Nososticta pilbara and other short‐range endemic species were absent from weeded reaches. As most odonates are univoltine, these adverse effects on local population size may affect species persistence.
6. Invasive macrophyte species may support a high diversity of native invertebrates, including endangered and short‐range endemic species. Furthermore, although hand‐weeding appeared to enable a greater diversity of species to co‐exist, the removal of a large biomass of macrophytes appeared to remove whole cohorts of insect populations from stream reaches, including endangered species. Removal of invasive macrophytes should not be implemented without understanding their effects on invertebrate assemblage composition and life‐cycles.

     

Freshwater mollusc assemblages and habitat associations in the Danube River drainage,Hungary

1. Native freshwater mollusc diversity has been declining over the past decades. For developing efficient conservation management plans for molluscs, it is especially important to identify areas with high native biodiversity.
2. The River Danube is one of the most important freshwater ecosystems in Europe and should receive special attention. The main objective of this work was to characterize the composition, diversity and conservation status of freshwater molluscs occurring in the Hungarian Danube River Drainage in five river habitat types (main channel of the Rivers Danube and Tisza, side channels of River Danube, tributaries of Rivers Danube and Tisza).
3. In total, 53 mollusc species were identified including 10 invasive species and 12 species of conservation concern. The main determining factors of mollusc composition were sediment characteristics, current velocity and oxygen content. Nitrate–nitrogen, ammonium–nitrogen, and calcium content also play a key role.
4. Overall, density, species richness and diversity showed significant differences between habitat types. The highest diversity values were detected in the side channels, but the highest proportion of threatened species was observed in the tributaries. The highest number and proportion of invasive species was detected in the main channel of the Danube. Most of the recorded invasive species were previously documented in side channels and the adjacent wetlands, but did not invade the tributaries.
5. Tributaries may provide refuges for native molluscs and could be considered as ‘source’ populations, which may be critically important in the regional maintenance of threatened species. Tributaries are still less disturbed and less invaded; and should be given priority in future conservation management plans.

Copyright © 2015 John Wiley & Sons, Ltd.     

Biodiversity value of remnant pools in an intermittent stream during the great California drought

1. In many intermittent streams, remnant pools persist after flow ceases and provide refuge for aquatic organisms able to tolerate stagnant water conditions. The conservation value of these pools may be greatly under‐appreciated, especially in regions with a Mediterranean climate, where perennial streams have been substantially modified or disturbed by human activities.
2. Fish, amphibians, aquatic reptiles, and aquatic invertebrates were sampled from 15 remnant pools and three seeps at Coyote Creek, California, USA, in the late summer of 2014, during the height of the most intense drought that California has experienced in 500 years. Patterns of vertebrate and invertebrate species richness and community composition were compared with abiotic factors (e.g. water quality and habitat size).
3. Thirteen vertebrate species and 172 invertebrate taxa were identified from remnant pools and seeps. Overall vertebrate richness and composition were not correlated with abiotic factors, but fish species richness increased with remnant pool size and depth. Invertebrate taxon richness increased with pool size. Invertebrate community composition differed by habitat type (pool versus seep) and gradients in composition were correlated with several abiotic factors (e.g. pool size, substrate, and canopy cover).
4. Remnant pools at Coyote Creek supported a full assemblage of native fishes and numerous imperilled taxa, including California red‐legged frogs and California floater mussels. Nearly all native fishes and imperilled taxa are absent from artificially perennial and urbanized reaches of Coyote Creek just a few kilometres downstream of the study area.
5. Remnant pools in intermittent streams should be a focus of conservation efforts in regions with a Mediterranean climate, especially during extreme droughts. Native fauna adapted to harsh intermittent flow regimes can thrive in these habitats, whereas non‐native taxa may fare poorly. Furthermore, remnant pools supported by deep groundwater sources, such as those along geological faults, may provide both ecological refuge and evolutionary refugia for freshwater biota.

     

Selecting areas to protect the biodiversity of aquatic ecosystems in a semiarid Mediterranean region using water beetles

• 1. In this work, carried out in the province of Murcia, a representative semi‐arid area of the Iberian Peninsula, water beetles were used as indicators to identify the aquatic ecosystems with the highest interest for conservation. For that purpose, an iterative algorithm of complementarity based on the richness of aquatic Coleoptera was applied. ‘Complementarity’ refers to the degree to which an area, or set of areas, contributes otherwise unrepresented attributes to a set of areas. This principle was used to maximize the number of species represented within a given number of areas.
• 2. Only the species subsets whose taxonomic status, presence and distribution in the study area are well known were used. In total, 146 species were included, of which 12 are Iberian endemics and 32 are rare species (found only in one grid cell in the study area).
• 3. The highest correlation was generally shown by species richness with endemic, rare and vulnerable species richness. Thus, basing conservation strategies on species richness appears to be an effective protocol.
• 4. To preserve the highest degree of biodiversity in the aquatic ecosystems of the study area, the following need to be protected: (a) headwater streams in the north west of the province; (b) the uppermost reaches of the Segura River; (c) hypersaline and coastal ramblas; (d) rock pools and coastal ponds.
• 5. The present network of Protected Natural Spaces in the study area does not include many of the aquatic ecosystems shown to have the highest biodiversity of beetles. However, the future European ‘Natura 2000’ network will protect the 10 grid cells of highest aquatic biodiverstity, or at least part of them.

Copyright © 2004 John Wiley & Sons, Ltd.